1. Field of the Invention
The invention relates to a vehicle operating state display device that displays the energy transmission state of a vehicle.
2. Description of Related Art
In recent years, a hybrid vehicle that runs by transmitting the output from two drive sources, i.e., an electric motor and an engine, to an axle via a transmission has been put into practical use. With this type of vehicle, the transmission state of energy between the engine, the electric motor, the axle, and a battery changes from moment to moment according to the running state of the vehicle. Therefore, this type of vehicle may be provided with an operating state display device that displays the current energy transmission state on a monitor of a car navigation system or an instrument panel or the like, as can be seen in Japanese Patent Application Publication No. 2010-167960 (JP 2010-167960 A), for example.
With this vehicle operating state display device, when the vehicle is being driven by the engine, for example, a display indicating that energy is being transmitted from the engine to the axle is shown. Also, when power is being generated by regenerative braking, a display indicating that energy is being transmitted from the axle to a motor-generator and from the motor-generator to the battery is shown.
However, with a hybrid vehicle such as that described above, if the frequency of engine vibration matches a specific frequency of the drive-train while the engine is starting, resonance will occur, which may result in torque shock and an abnormal noise referred to as so-called rattling, due to gears in the transmission striking each other. Therefore, in this kind of hybrid vehicle, so-called push control of the electric motor that reduces backlash in the transmission by applying torque from the electric motor is performed in an attempt to prevent or reduce this kind of torque shock and abnormal noise. Depending on this push control, a certain degree of torque is transmitted from the electric motor to the axle, so with an operating state display device such as that described in JP 2010-167960 A, a display indicating that energy is being transmitted from the electric motor to the axle is shown.
However, if there is a display indicating that energy is being transmitted to the axle while the vehicle is stopped by a brake operation being performed, the driver may mistakenly think that unnecessary consumption of energy is occurring because driving force is being generated even though the vehicle is not moving. Also, with control other than push control as well, if, while the vehicle is stopped, torque is generated for a purpose other than moving the vehicle, the driver may similarly mistakenly think that unnecessary consumption of energy is occurring due to the transmission of energy to the axle according to that generation of torque being shown.